The present invention relates to an improved volume limiting chamber for use in the intravenous set.
Intravenous sets for the administration of parenteral solution to a patient typically include a piercer for insertion into a parenteral solution container, flexible tubing for transporting the parenteral solution from the container to the patient, a first or lower flow control clamp which acts on the flexible tubing to control the flow rate of the parenteral solution, and a needle adapter to which an intravenous needle is attached. The flow rate is determined by a flow meter such as a drip chamber positioned upstream of the lower clamp. The intravenous set may also include a volume limiting chamber positioned between the piercer and the drip chamber and a second or upper flow control clamp positioned upstream of the volume limiting chamber. The volume limiting chamber is used to precisely control the volume of parenteral solution administered to the patient.
The volume limiting chamber is normally designed to automatically shut off after a measured volume of parenteral solution is fed to the patient. This is accomplished in many intravenous sets by a membrane valve mounted in the bottom of the volume limiting chamber. Basically, the membrane valve comprises a material which when wet will pass parenteral fluid but will not pass air at normal intravenous administration pressures. In using an intravenous set of this type, both the upper and lower control clamps are closed and the piercer is inserted into the outlet of a parenteral solution container. The upper flow control clamp is then opened and the volume limiting chamber partially filled with parenteral solution. After the upper flow control clamp is again closed, the set must be primed. This is accomplished by opening the lower flow control clamp, squeezing the drip chamber and then closing the lower flow control clamp. The drip chamber is then released and will partially fill with parenteral solution. This priming step is repeated until the drip chamber is approximately one-half filled. The lower flow control clamp must be opened during the priming operation so that the membrane valve will not be damaged. This priming operation is tedious and time consuming and runs the risk of damaging the delicate membrane valve unless strictly followed.
Intravenous sets are also known in which the volume limiting chamber is automatically shut off by a float having a very thin, flexible diaphragm adapted to seat against a valve seat and close off the flow of liquid and air after a measured volume of solution is fed to the patient. Intravenous sets of this type can be primed without repeatedly opening and closing the lower flow control clamp. However, since the diaphragm only seats against the valve seat after the measured volume of solution is fed to the patient, the parenteral solution is not filtered during administration.
Accordingly, it is an object of the present invention to provide an improved volume limiting chamber.
It is another object of the present invention to provide an improved automatic shut off valve for use in an intravenous set.
It is a further object of the present invention to provide an improved volume limiting chamber having an automatic shut off valve.
It is still a further object of the present invention to provide an improved volume limiting chamber having an automatic shut off valve in which the intravenous set can be primed by squeezing and releasing the flexible drip chamber without simultaneously opening and closing the flow control clamps.
Yet another object of the present invention is to provide an improved volume limiting chamber having a membrane valve in which the membrane valve is mounted so that air can enter the volume limiting chamber from the drip chamber around the periphery of the membrane valve during priming.
A still further object of the present invention is to provide an improved membrane filter for use in an intravenous set.